1. Field of the Invention
The present invention relates to a radio frequency transceiver apparatus for performing a change-over between a whip antenna (movable antenna) and a built-in antenna (internal antenna) in a portable communication device used in a moving body such as an automobile.
2. Description of the Prior Art
In FIG. 1, which is a block diagram showing a conventional radio frequency transceiver apparatus, the numeral 1 denotes an extensible/retractable whip antenna; numeral 2 denotes a built-in antenna; numeral 3 denotes a change-over switch actuator which operates according to the retraction and extension of the whip antenna 1; numeral 4 denotes a double-throw change-over switch which is actuated for change-over operation by the change-over switch actuator 3; and numeral 5 denotes a radio section composed of first and second radio sections 5a, 5b which are each brought into connection with either the whip antenna 1 or the built-in antenna 2 through the double-throw change-over switch 4 and feeders 6 serving as coupling means.
The first radio section 5a constitutes a first configuration of the transceiver means for processing RF (radio frequency) signals of a low level, while the second radio section 5b constitutes a second configuration of the transceiver means for processing RF signals of a high level relative to the low level.
When the whip antenna 1 is extended, the whip antenna and the first radio section 5a are connected and the built-in antenna 2 and the second radio section 5b connected. On the other hand, when the whip antenna 1 is retracted, it is disconnected from the first radio section 5a and the built-in antenna 2 is disconnected from the second radio section 5b and connected to the first radio section 5a.
Numeral 7A denotes a housing which houses therein the whip antenna 1, built-in antenna 2, change-over switch actuator 3, double-throw change-over switch 4 and radio section 5. The housing 7A can be mounted in a moving body such as an automobile.
The operation of such conventional radio frequency transceiver apparatus will now be described. When the whip antenna 1 is extended, the double-throw change-over switch 4 is switched from the built-in antenna 2 side to the whip antenna 1 side by the change-over switch actuator 3, so that the whip antenna 1 and the first radio section 5a are connected and the built-in antenna 2 and the second radio section 5b connected through feeders 6.
On the other hand, when the whip antenna 1 is retracted, the double-throw change-over switch 4 is switched from the whip antenna 1 side to the built-in antenna 2 side by the change-over switch actuator 3, so that the built-in antenna 2 and the first radio section 5a are connected through feeders 6. At this time, the second radio section 5b is disconnected from both antennas.
The change-over switch actuator 3 operates mechanically according to extension and retraction of the whip antenna. A contact piece (not shown) thereof actuates a change-over lever of the double-throw change-over switch 4 to change over the same switch.
A transmitter and a receiver are incorporated in the first radio section 5a, while a receiver is incorporated in the radio section 5b. When the reception level is low, there is performed diversity reception wherein the whip antenna 1 is extended and used for both transmission and reception, while the built-in antenna 2 is used for reception only. On the other hand, when the reception level is high, the whip antenna 1 is retracted and only the built-in antenna 2 is used for transmission and reception.
Since the conventional radio frequency transceiver apparatus is constructed as above, the whip antenna 1 when retracted is disconnected from all the circuits and so it does not function as antenna at all. Moreover, for change-over between the whip antenna 1 and the built-in antenna 2 it is necessary to use the change-over switch actuator 3 in addition to the double-throw change-over 4. This structure results in an increase in the number of components causes problems such as insertion loss and deterioration of VSWR (voltage standing wave ratio).
A closely similar art to the above prior art, reference is here made to a portable radio device invented by Mr. Tamura, filed with the Japanese Patent Office by Nippon Electric Company, Limited on Aug. 30, 1986 and laid open as Japanese Patent Laid-Open No. 60628/88 on Mar. 16, 1988.